1. Field of the Invention
The present invention relates to a photocatalytic active carbon capable of demonstrating a stable deodorizing and adsorbing ability for a prolonged period of time by combining the adsorbing action of active carbon with the decomposing and sterilizing action of a photocatalyst, and in particular to colored photocatalytic active carbon and coloring active carbon including the photocatalytic active carbon, which while maintaining the adsorbing action and the decomposing and sterilizing action, comes to be rich in color variations and capable of improving visual design and handling by subjecting the surface of the active carbon to coloring treatment and/or treatment with a compound having coloring or discoloring properties upon hydration, and to a deodorant and adsorption product using them.
2. Description of the Related Art
Active carbon is carbon whose ability to adsorb gas, pigments etc. has been improved by subjecting a starting material (material of active carbon) such as wood, sawdust, dry-distillated wood, charcoal, coconut shell or lignin to special treatment (activating treatment), and active carbon is the most widely used adsorbent at present in the field of deodorants and adsorption products, such as water purification, deodorants in refrigerators or shoe cupboards, filters in an air cleaners, etc. because of its low price and its high ability to adsorb odor components such as household odors, VOC gas causing sick house, such as formalin, ethyl benzene or xylene, and adsorbed components such as water.
However, the adsorption of such active carbon is non-stationary and governed by adsorption equilibrium, so that once a predetermined amount of adsorbed components and water are adsorbed, the active carbon looses its adsorption ability and comes to be in an inactivated state.
To regenerate the adsorption ability of active carbon in this inactivated state, the active carbon is subjected to heat treatment or treatment with inert gas at high temperatures in order to remove the adsorbed components and water from micropores on the surface of the active carbon.
When adsorbed components are adsorbed strongly into the micropores on the surface of the active carbon, the active carbon is heated at a high temperature of about 500 to 800xc2x0 C. for several hours thereby carbonizing the adsorbed components, and in the presence of water vapor, these carbonized materials on the surface are gasified by heating at 900 to 1200xc2x0 C. for several hours, whereby the active carbon is activated for regeneration.
However, these methods of regenerating active carbon are problematic because the regeneration cost is increased due to the necessity for a special regeneration furnace, and the concentration of water vapor, the activating temperature, the activating time etc. in the regeneration furnace are hardly regulated; thus causing a loss in several to several tens % of the adsorption ability every time active carbon is regenerated
Accordingly, these regeneration treatment methods are not used for a deodorant or adsorption product using conventional active carbon, and in almost all cases, the whole of the deodorant or adsorption product, or the active carbon therein, is exchanged with a new one.
However, the active carbon has a relatively high adsorption ability as described above, to reach a saturated state in a short time, and therefore, the active carbon should be exchanged frequently, but this exchange is very troublesome in circumstances where it is actually used.
Further, there is the problem that the active carbon just after activating treatment cannot be visually distinguishable from the one in a saturated state, and thus the time for exchange cannot be judged with the naked eyes, and for this reason and owing to the troublesome operation of exchange, the active carbon is often left even after the time for exchange.
Further, the active carbon is black and thus inferior in design, and thus almost all deodorants or adsorption products using active carbon commercially available at present are devised such that their active carbon cannot be seen from the outside by encapsulating the active carbon in a package or box. Thus this not only makes it further difficult to judge the time of exchange with the naked eyes, but also deprives the active carbon of the opportunity thereof to contact with the air so that the good adsorption ability of the active carbon cannot be sufficiently demonstrated.
These problems seem to be solved by simply coloring the active carbon, but the surface of the active carbon is a mass of carbon onto which a hydrophilic coating is hardly applied, and even if coated with the coating, the active carbon is very poor in coloring because of its original black color, thus making achievement of various color variations is difficult.
The means of decomposing adsorbed components captured in micropores on the surface of active carbon is studied and developed very recently by mixing active carbon with a photocatalyst such as titanium dioxide or by permitting a photocatalyst to be carried via a binder such as an adhesive on the surface of active carbon.
That is, the active carbon mixed with the photocatalyst or having the photocatalyst carried thereon is studied extensively at preset because even if such active carbon reaches saturated with adsorbed components captured in the micropores on the surface of the active carbon, the active carbon can decompose the adsorbed components by the photocatalyst upon irradiation of the active carbon with sunrays or lights containing UV rays from an incandescent lamp, thus regenerating the adsorption ability of the active carbon in order to maintain and secure the adsorption action thereof for a prolonged period of time.
However, when the active carbon and photocatalyst are mixed, the photocatalyst is apart from adsorbed components on the surface of active carbon, thus lowering the action of decomposing the adsorbed components, and the photocatalyst is a powder easily scattered and inferior in handling and recovery, and the scattered photocatalyst scatters UV rays to further lower the decomposition action.
Further, the active carbon and the photocatalyst are hardly mixed because of a difference in specific gravity and particle diameter, and as a result there is the problem that qualities are varied and the desired adsorption and photocatalytic action cannot be achieved.
On the other hand, when the photocatalyst is carried via a binder such as an adhesive on the surface of active carbon, the photocatalyst is embedded in the binder, or the micropores on the surface of active carbon are covered with the binder, and as a result there is the problem that the action of the photocatalyst to decompose the adsorbed components is weakened, and the adsorbing ability of active carbon is reduced, and further there is the problem that the binder itself is subjected to the decomposition action of the photocatalyst and thus exfoliated and released from the surface of the active carbon.
Further, there is the problem that the decomposition action of the photocatalyst is directed to only the adsorbed components based on organic materials so that when water is adsorbed, there is no or less effect.
This adsorbed water can be removed by the simple treatment such as slightly heating active carbon or drying it under sunrays, but as described above, the active carbon even just after activation cannot be distinguished with the naked eyes from the one in a saturated state (i.e. the one having lost the adsorption ability), and therefore, the active carbon after saturated with water is often still left in a refrigerator.
As a result of extensive study for solving the problems described above, the present inventors found that a coating of a photocatalyst is formed and carried by means of vapor deposition on the surface of active carbon, whereby the photocatalyst can be made close to micropores on the surface of active carbon, and by means of vapor deposition without using a binder or the like, a reduction caused by imbedding, in the action of the photocatalyst to decompose adsorbed components can be prevented, and the coating of the photocatalyst is so thin that even if the micropores on the surface of active carbon is covered with the coating, the adsorption ability of active carbon is hardly deteriorated.
Further, the present inventors found that by covering the surface of active carbon with a coating of a photocatalyst, the active carbon can be easily subjected thereon to coloring treatment, whereby the active carbon can have various color variations to improve design.
The present inventors found that by using particularly TiO2 as an essential ingredient in the photocatalytic coating, the surface of the active carbon after vapor deposition treatment can be made gray or white, and the coloring thereof upon coloration can thereby be significantly improved.
Further, the present inventors found that after the surface of active carbon is covered with the photocatalytic coating, a compound having coloring or discoloring properties upon hydration is carried thereon, whereby the surface of the active carbon is gradually colored or discolored depending on the amount of water adsorbed, and as a result, the time for exchange of the active carbon and the time for regeneration by drying can be easily known and the handling can thereby be improved.
The prevent invention is completed on the basis of the findings described above, and an object of the present invention is to provide a photocatalytic active carbon capable of demonstrating a stable deodorizing and adsorbing ability for a prolonged period of time by forming and carrying a coating of a photocatalyst by means of vapor deposition, and a further object is to provide colored photocatalytic active carbon and coloring active carbon including the photocatalytic active carbon, which while maintaining the adsorbing action and the decomposing and sterilizing action, comes to be rich in color variations and capable of improving visual design and handling by subjecting the surface of the active carbon to coloring treatment and/or treatment with a compound having coloring or discoloring properties upon hydration, as well as a deodorant and adsorption product using them.
To achieve the object, the photocatalytic active carbon of the present invention forms and carries a coating of a photocatalyst by means of vapor deposition on the surface of active carbon.
That is, the photocatalytic active carbon capable of exhibiting a deodorizing and adsorbing ability stably for a long time can be obtained by forming and carrying a coating of the photocatalyst on the surface of active carbon.
In the photocatalytic active carbon thus obtained, the micropores on the surface of active carbon are made close to the photocatalyst, and the photocatalyst is carried by means of vapor deposition without using a binder or the like, a reduction caused by imbedding, in the action of the photocatalyst to decompose adsorbed components can be prevented, and the coating of the photocatalyst by means of vapor deposition is so thin that even if the micropores on the surface of active carbon is covered with the coating, the adsorption ability of active carbon is hardly deteriorated.
Hereinafter, the photocatalytic active carbon of the present invention is described in more detail.
As described above, the photocatalytic active carbon of the present invention is obtained by forming and carrying a coating of a photocatalyst by means of vapor deposition on the surface of active carbon.
The active carbon used in the photocatalytic active carbon of the invention is not particularly limited, and can make use of conventional active carbon used in industrial catalytic carriers and deodorants and recovery of organic solvents.
The materials of the active carbon are not particularly limited either, and can make use of known materials of active carbon, such as wood, sawdust, dry-distillated wood, charcoal, coconut shell and lignin, among which preferably used is a coconut shell which is easily available and inexpensive and have high absorptivity.
The photocatalytic active carbon of the present invention forms and carries a coating of a photocatalyst by means of vapor deposition on the surface of the active carbon, and the photocatalyst is not particularly limited insofar as it can bring about catalytic reaction upon light absorption to decompose adsorbed materials adsorbed on the active carbon.
In the photocatalytic reaction, light energy is added to the reaction system so that in the reaction system, there are two cases where Gibbs"" free energy is decreased or increased, and generally the latter may be regarded as being different from the photocatalytic reaction, but in the photocatalytic reaction in the present invention, there is no necessity for particular discrimination between the two.
Specifically, the photocatalyst includes e.g. TiO2, ZnO, SrTiO3, CdS, CdO, CaP, InP, In2O3, CaAs, BaTiO3, K2NbO3, Fe2O3, Ta2O5, WO3, SaO2, Bi2O3, NiO, Cu2O, SiC, SiO2, MoS2, MoS3, InPb, RuO2 and CeO2, and in the present invention, at least one member selected from these photocatalysts can be used.
In the present invention, the starting material of the photocatalyst carried on the surface of active carbon is not limited to the photocatalysts described above, and even a starting material not having a photocatalytic action can be used insofar as it can be converted by means of vapor deposition described later into a coating of a photocatalyst to be formed and carried on the surface of activated carbon.
The photocatalytic active carbon of the present invention carries the photocatalyst by means of vapor deposition on the surface of active carbon, but the vapor deposition means is preferably the so-called thin film-making techniques such as sputtering, glow discharge, thermal vapor deposition, chemical vapor deposition or ion plating, and in the present invention, at least one or two technique selected from the vapor deposition means can be used, among which preferably used is the thermal vapor deposition means which is easy and economical with high efficiency and a high rate of vapor deposition.
In the vapor deposition means in the present invention, the amount of the photocatalyst formed and carried on the surface of active carbon is not particularly limited, and may be suitably determined depending on the intended use, place etc., and generally the photocatalyst may be carried in an amount of 1 to 200 parts by weight relative to 100 parts by weight of active carbon.
A predetermined amount of the photocatalyst is formed and carried more preferably twice or more than once by vapor deposition in order to permit the photocatalyst to be more strongly carried on the surface of the active carbon.
In the photocatalytic active carbon of the present invention, the photocatalyst carried on the surface of the active carbon particularly preferably including TiO2 as an essential ingredient.
This is because TiO2 is superior as a photocatalyst in the ability to decompose adsorbed components, and further because by forming and carrying TiO2 on the surface of active carbon, the surface of the active carbon turns gray or white, whereby the black image of the active carbon is eliminated, and the coloring ability of the colored photocatalytic active carbon or coloring active carbon of the present invention described later is significantly improved.
Accordingly, the photocatalytic active carbon of the present invention preferably includes TiO2 as an active ingredient in the photocatalyst carried on the surface of the active carbon, and specifically the amount of TiO2 is preferably 30 to 100% by weight, more preferably 50 to 100% by weight of the photocatalytic coating formed and carried on the surface of the active carbon.
Hereinafter, the colored photocatalytic active carbon of the present invention is described in more detail, but the features overlapping with those described above for the photocatalytic active carbon of the present invention are omitted in the following description.
The colored photocatalytic active carbon of the present invention is obtained by which the photocatalytic active carbon of the present invention subjected to coloring treatment.
That is, the photocatalytic active carbon of the present invention is obtained by the active carbon covered thereon with a coating of the photocatalyst, so the carbon on the surface of the active carbon is bared, and thus the surface can be easily subjected to various kinds of coloring treatment, whereby the active carbon can have various color variations to improve design.
Because the active carbon including TiO2 as an essential ingredient in the photocatalytic coating is gray or white after the vapor deposition, the coloring of the active carbon upon coloration is significantly improved.
Accordingly, the coloring agent used in coloring treatment of the colored photocatalytic active carbon of the present invention is not particularly limited, and can make use of a conventional coloring agent used in aqueous coatings, oil coatings or synthetic resin coatings, and the coloration method is not particularly limited, and means such as brushing, spray coating, electrostatic coating, flow coating or dipping coating can be used.
In the colored photocatalytic active carbon of the present invention, the micropores on the surface of the active carbon can be embedded in a relatively thick coating of the coloring agent, to deteriorate the adsorption ability of the active carbon, and thus the coating of the coloring agent is preferably as thin as possible.
Accordingly, the coloring treatment in the present invention is conducted preferably by means of vapor deposition, preferably by means of vapor deposition using a dye or pigment in consideration of stability.
That is, a dye or pigment coating formed by means of vapor deposition is very thin so that even if the micropores on the surface of the active carbon are covered with said coating, the adsorption ability of the active carbon is hardly deteriorated.
A description of the vapor deposition means used herein is omitted because the same means as described above can also be preferably used.
Specifically, the dye or pigment includes e.g. various dyes and pigments, preferably pigments stable to the action of the photocatalyst.
Specifically, the pigment includes e.g. white pigments such as titanium dioxide, zinc oxide, zinc sulfide, lithopone, lead pigment, antimony oxide, zirconium oxide and zircon, extender pigments such as hydrous magnesium aluminum silicate, calcium carbonate, barium sulfate, silicate, potassium aluminosilicate and hydrated alumina, chromatic pigments such as an iron oxide pigment, lead chromate, lead molybdate, cadmium pigment, a synthetic metal oxide mixture and Prussian blue, special pigments such as zinc yellow, basic zinc chromate, strontium chromate, red lead, copper oxide (I), calcium plumbate, basic lead silicochromate, white molybdate, modified barium metaborate, zinc phosphate and pearl essence, and metal pigments, and the colored photocatalytic active carbon of the present invention can make use of at least one member selected from these pigments.
Hereinafter, the coloring active carbon of the present invention is described in detail, but a description of features overlapping with those of the photocatalytic active carbon or colored photocatalytic active carbon of the present invention is omitted.
The coloring active carbon of the present invention has the feature that a compound having coloring or discoloring properties upon hydration has been carried on the photocatalytic active carbon or colored photocatalytic active carbon of the present invention described above.
That is, the photocatalytic active carbon or colored photocatalytic active carbon of the present invention described above further carries a compound having coloring or discoloring properties upon hydration carried thereon, whereby the surface of the active carbon is gradually colored or discolored depending on the amount of water adsorbed, and as a result, the time for exchange of the active carbon and the time for regeneration by drying can be easily known, and handling can be improved.
In particular, the active carbon including TiO2 as an essential ingredient in the photocatalytic coating is gray or white after the vapor deposition, and thus the compound having coloring or discoloring properties upon hydration on the active carbon is significantly improved.
The compound having coloring or discoloring properties upon hydration on the coloring active carbon of the present invention is not particularly limited insofar as it is a compound which has a property of binding with water of crystallization, water in a molecular form or an inclusion water molecule or forming a complex with a water molecule and which has coloring or discoloring properties upon binding with a water molecule.
Specifically, the compound having such properties includes e.g. CoCl2 (blue compound which upon hydration, becomes red CoCl2.6H2O), CoBr2 (green compound which upon hydration, becomes reddish purple CoBr2.6H2O), CrCl3 (purple compound which upon hydration, becomes green CrCl3.6H2O), CuCl2 (yellowish brown compound which upon hydration, becomes green CuCl2.2H2O), FeBr3 (reddish brown compound which upon hydration, becomes green FeBr3.6H2O), NiCl2 (yellow compound which upon hydration, becomes green NiCl2.6H2O), and NiSO4 (yellow compound which upon hydration, becomes green NiSO4.6H2O).
In the coloring active carbon of the present invention, the method of carrying the compound is not particularly limited, and for example, a means such as brushing, spray coating, electrostatic coating, flow coating or dipping coating can be used.
In the coloring active carbon of the present invention, the micropores on the surface of the active carbon may be embedded in a coating of the compound, to deteriorate the adsorption ability of the active carbon, and thus the coating of the compound is preferably as thin as possible.
Accordingly, the compound in the present invention is carried particularly preferably by means of vapor deposition.
That is, a coating formed by means of vapor deposition is very thin so that even if the micropores on the surface of the active carbon are covered with the coating, the adsorption ability of the active carbon is hardly deteriorated.
A description of the vapor deposition means used herein is omitted because the same means as described above can also be preferably used.
The deodorant and adsorbent products of the present invention uses at least one member selected from the group consisting of the photocatalytic active carbon, colored photocatalytic active carbon and coloring active carbon of the present invention, and it is a product embodying the action possessed by the photocatalytic active carbon, colored photocatalytic active carbon or coloring active carbon of the present invention, and examples thereof include a deodorant adsorbing and decomposing nasty odors in a room, a toilet, a refrigerator or an automobile for a long time, and a water-purifying agent for water purification in a lavatory cistern or for preventing occurrence of bacteria.
Because the product have various color variations, it can also be applied to a paper, a film made of resin, or building materials such as shoji paper, wall paper and fusuma paper to be carried on a sheet, and the product is wide applicability as compared with conventional active carbon because the product, even if carried on the surface of interior ornaments such as interior products and household goods, does not deteriorate their design.